1. Field of the Invention
The present invention relates to electrostatic speakers (or capacitor speakers) constituted of parallel planar electrodes and diaphragms.
The present application claims priority on Japanese Patent Application No. 2009-226383, the content of which is incorporated herein by reference.
2. Description of the Related Art
Patent Document 1 (i.e. Japanese Patent Application Publication No, 2007-318554) discloses an electrostatic speaker in which a film-shaped diaphragm having conductivity is interposed between two planar electrodes which are disposed in parallel with a gap therebetween. A bias voltage is applied to a diaphragm while a voltage is applied to electrodes, thus causing an electrostatic force on the diaphragm. When an applied voltage of electrodes varies, an electrostatic force of a diaphragm varies so as to cause a displacement in the diaphragm. When an applied voltage of electrodes varies in response to an audio signal, displacements repeatedly occur on a diaphragm to vibrate, thus producing sound waves in response to an audio signal. That is, an electrostatic speaker emits sound waves to the external space via electrodes.
Patent Document 1 adopts a power-supply method in which an electric power is supplied to a diaphragm via a conducting wire soldered to the diaphragm. It discloses another power-supply method in which a crimp terminal (or a solder-less terminal) connected with a conducting wire is fixed with screws to a pair of metal plates sandwiching a diaphragm.
Diaphragms are produced by depositing metals on synthetic-resin films, the thickness of which ranges from several micrometers to several tens of micrometers. For this reason, diaphragms having a small thickness are easily affected by heat, which occurs during soldering of conductive wires; hence, a high technique for soldering conductive wires onto diaphragms is needed. The power-supply method, in which a conducting wire is fixed to a diaphragm with a screw, does not cause heat to affect the diaphragm; however, this requires a time-consuming job for attaching and detaching conducting wires with diaphragms by use of drivers.